The invention relates to a fluid flow device such as a micropump comprising at least a first plate, a second plate, an intermediate plate disposed between said first and second plates, a pump chamber defined by said first plate and said intermediate plate, and inlet and outlet control members communicating with said pump chamber, some inlet and outlet ducts passing through one of said first and second plates, said inlet control member being a non-return valve made up of a moving member and a membrane-forming portion connecting said moving member to the remainder of said intermediate plate, interposed between the inlet duct and the pump chamber, and, by virtue of its resilience, enabling said valve to move between a closed position and an open position, said moving member having an orifice passing therethrough between its first and second ends, said valve being shaped in such a manner that, in said open position, the moving member does not prevent liquid from flowing from said orifice towards said pump chamber, and the second end of the moving member being shaped in such a manner that, in said closed position, it provides sealed contact with that one of the plates that forms the seat of the valve.
For example, but in non-exclusive manner, such a device constitutes a micropump for medical use which regularly delivers a controlled quantity of medication. The manufacture of such micropumps is based on technologies for micro-machining silicon or any other material that can be machined by etching using photolitographic techniques. For the particular application mentioned above, and also in other cases, it is necessary to provide an inlet control member enabling the micropump to be self-priming. The micropump is controlled by varying the volume of its pump chamber (alternating decreases and increases of volume), e.g. by means of control using a piezoelectric actuator.
European patent application 95 905 674.9 describes such a self-priming micropump. However, the inlet valves described in that document are not easy to make.
European patent application 90 810 272.6 describes a micropump having an inlet member that forms a non-return valve, but that does not enable the pump to be self-priming.
The object of the present invention is to provide a fluid flow device such as a micropump having an inlet control member that enables said device to be self-priming in reliable manner, with the member being easy to manufacture.
According to the invention, this object is achieved by the facts that the moving member is situated in the major portion of the thickness of said intermediate plate, that the membrane-forming portion is situated close to the other one of the plates, and that said orifice presents a volume that is limited.
It will be understood that the liquid inlet control member included in the device of the present invention constitutes a non-return valve of the seated-valve type. The non-return valve has a membrane portion whose resilience makes it possible to open and close the valve, and a moving member that surrounds an orifice through which liquid can flow. At one of its ends, the moving member also has means for ensuring that said inlet valve is sealed in its closed position, i.e. that the moving member bears in sealed manner against one of the plates adjacent to the valve, this plate forming the seat of the valve.
According to an essential characteristic of the invention, in order to avoid the moving member obstructing the pump chamber, provision is preferably made for the first end of the moving member adjacent to said membrane-forming portion to be provided with at least one abutment element designed to limit the movement of said valve from the closed position towards the open position, the free end of said abutment element coming into contact with the plate situated close to the membrane-forming portion in said open position without said abutment element preventing liquid from flowing from said orifice towards said pump chamber.
The invention will be better understood and secondary characteristics and advantages thereof will appear on reading the following description of embodiments given below by way of example.